It has long been known that an increase in the speed and efficiency of many chemical reactions can be induced by subjecting the substances involved to greatly increased pressure and temperature conditions. At one time it was popular to develop the desired conditions by utilizing autoclaves to confine a batch of the material to be treated which, when heated, gave off vapors and pressurized the container. Alternatively, tanks were pressurized with pumps while being heated. These types of systems have been falling into disuse because of their lack of capacity due to the batch nature of the process, and because of the mechanical maintenance intensity inherent in the use of specialized pumps and outlet throttling devices.
The autoclave and pumped pressure tanks to create high pressure and temperature conditions have generally been replaced by the art of using a hydraulic column to develop the desired conditions. The teachings in this art are typified by Bauer U.S. Pat. No. 3,449,247; Lawless U.S. Pat. No. 3,606,999; Titmas U.S. Pat. No. 3,853,759; and McGrew U.S. Pat. No. 4,272,383.
However, the hydraulic column art has not taught the ability to operate, or appreciated the advantages of operating, at the state of water known as the threshold supercritical point of temperature and pressure. As is known in the art this threshold point is the point of temperature and pressure at which the phase barrier between water and vapor no longer exists. Supercritical water, steam and high pressure water exist simultaneously and gases, such as oxygen, water, and oils are fully miscible in all proportions and inorganic salts are virtually insoluable. This condition begins to occur at a pressure of 3207 psi and a temperature of 706.degree. F.
Furthermore, these existing hydraulic column methods lack acceptable means to achieve sustained supercritical conditions. For example, the Bauer patent teaches that if the fundamental energy in the fluid stream is insufficient, fuel, in the form of combustible refuse, must be added to induce wet combustion. However, the addition of such combustible refuse is impractical and unmanageable since the inconsistent and irregular BTU content of combustible refuse does not enable one to provide a uniform energy control on a continuous basis to sustain the supercritical condition. Similarly, the Titmas patent is limited to only certain chemical reactions in that it teaches the advantages of limiting combustion by restricting the process to oxygen inherently present in the material. For many processes which can take place at the supercritical point, additional oxygen will be required. Furthermore, those processes which teach the addition of steam heat, such as taught in the Titmas patent, cannot be operated at the supercritical point since steam condenses at that point and no net heat is injected.
Likewise, the teachings of the McGrew patent fall short of suggesting a process which can be carried on at the threshold of the supercritical conditions. The McGrew patent teaches the addition of combustible gases in the downdraft of the hydraulic column in an attempt to sustain the heat needs by substantially complete wet combustion of the organic content of the material to be treated. Such addition of oxygen in the downdraft cannot result in a controlled reaction at the supercritical threshold point because the downdraft heats too quickly resulting in a loss of peak pressure and increased heat losses to the strata. The result of the McGrew process is a less than average contaminent destruction since the wet combustion is initiated at too low a temperature, a temperature far below that of the supercritical range. Furthermore, since the downdraft of McGrew is heated, it loses its advantageous effect of cooling the updraft.
In short, none of the hydraulic column prior art is capable of efficient operation at the threshold point of the supercritical range. Nor does any of this art recognize the fact that even if it could operate at supercritical conditions, the inorganic salts, inherently present in contaminated waters, could be readily separated in the hydraulic column on a continuous basis.
The only art of which I am aware that even considers the supercritical range and the advantages thereof is Modell U.S. Pat. No. 4,558,199. The Modell patent does not teach the use of a hydraulic column to effect the necessary pressure but rather utilizes pumps to induce pressure in an above-the-ground vessel. Actually, the Modell patent teaches pressurizing the vessel to a much higher pressure than needed at the supercritical threshold point with wet combustion sustaining a higher temperature than that needed at the threshold point. Modell thus operates at temperatures and pressures well into the supercritical range. This excessive and inefficient energy demand is necessary because Modell teaches conducting the reacted material to a separate conventional separation chamber during which time the material is inherently cooling. Once at the separation chamber, the material is hopefully still in the supercritical range so that particulates can settle out. However, Modell does not teach any means of separating the particulates from the high pressure environment on a continuous basis. This problem remains unsolved as the pressure drop from at least 3234 psi cannot be controlled or contained by known throttling devices as the particulates and gas bubbles flashing from the supercritical fluid effectively move through the throttling device at sonic velocities eroding and destroying the device itself.
The process according to the Modell patent is also plagued by problems inherent in essentially all nonhydraulic column reactors and in particular, the problem of having to efficiently pump abrasive and hostile waste materials to an extremely high pressure which cannot economically be done in any high quantities. Thus, Modell would operate with possibly lower quantities of higher concentrated wastes, such as the 5000 to 25000 parts per million concentration he discusses, whereas most waste streams, in need of continuous processing in high volumes, contain only 300 to 3000 parts per million of organic contaminants.
As a result of the shortcomings of the prior art, the human environment continues to degenerate due to the accumulation of toxic and petrochemical wastes wherein no present method of ultimate destruction is practicable and many production processes are inefficient by excessive use of energy, batch processing, or high pressure containment problems. For example, waste oils mixed with brakish water exhibiting a high ratio of Chemical Oxygen Demand (C.O.D.) compared to its Biochemical Oxygen Demand (B.O.D.) are not amenable to conventional biological treatment and can include hundreds of individual chemicals determined to be carcinogenic or otherwise toxic. Some of these materials are not now included on the Environmental Protection Agency's list for control not because they do not represent a clear and present danger to health, but because there is no practical method for their destruction. The energy content inherent in the typical waste stream is neither sufficiently consistent, nor adequate, to sustain even existing hydraulic column processes.